1. Field of the Invention
This invention relates to a target determination apparatus and more particularly to a target determination apparatus, which determines as to whether or not the target is a human being.
2. Description of the Related Art
A system for measuring the distance between a vehicle and another vehicle ahead and the relative velocity therebetween using a radar (radio detecting and ranging) technology and holding the distance between the vehicle and the other vehicle ahead based on the measurement values is available as a vehicle driving support system.
FIG. 8 is a block diagram to schematically show the main part of a radar according to a related art for measuring the distance and the relative velocity between the vehicle and the other vehicle ahead. In the figure, numeral 1 denotes a radar. The radar 1 includes a microcomputer 2, a transmission antenna 3, a pulse transmission unit 4, a reception antenna 5, and a delay detection unit 6. The pulse transmission unit 4 emits an electromagnetic pulse from the transmission antenna 3. The electromagnetic wave emitted from the transmission antenna 3 and striking a target T (for example, the vehicle ahead) is again radiated (namely, reflected) in every direction at the target T and only a part of the electromagnetic wave is returned in the original direction. The reception antenna 5 receives a very small amount of the returned electromagnetic pulse.
The delay detection unit 6 is connected to the pulse transmission unit 4, to keep track of the electromagnetic pulse emitting timing, and is connected to the reception antenna 5, to keep track of the reflection pulse receiving timing, and can detect the time between emitting the electromagnetic pulse and receiving the reflection pulse (namely, delay time) Letting the delay time be Δt, distance R to the target T can be found as cΔt/2 (where c is the speed of light and is 3×108 m/s).
The microcomputer 2 can be connected to the delay detection unit 6, to acquire data concerning the delay time Δt. The microcomputer 2 includes a distance calculation unit 2a and a relative velocity calculation unit 2b. The distance calculation unit 2a finds the distance R to the target T based on the data concerning the delay time Δt provided by the delay detection unit 6. The relative velocity calculation unit 2b monitors the distance R found by the distance calculation unit 2a in time sequence and finds relative velocity Δv of the target T based on the change of the distance R with time. Thus, the radar technology is applied and the radar 1 is installed in a vehicle, whereby an excellent driving support system can be realized.
As systems using the radar technology, a preventive safety system for previously detecting a pedestrian and preventing an accident from occurring is proposed in addition to the driving support system. One preventive safety system uses a radar to detect a pedestrian out of the visual range of headlights in the night and a pedestrian on a crosswalk and informs the driver of the presence of the pedestrian.